By far the most frequently used technique for implantation of prosthetic valves such as aortic and mitral valves is to use pledgeted mattress sutures. The term xe2x80x9cmattressxe2x80x9d refers to the fact that each suture passes through the fabric suturing ring or cuff of the prosthetic valve and through the tissue to which the prosthesis will be attached at two points separated, for example, by a gap of about 4 to 8 mm and more preferably between about 4 to 6 mm. To facilitate this, the piece of suture material has two surgical needles pre-attached, one at each end. The term xe2x80x9csuturexe2x80x9d refers to the composite of suture material and needles. The suture material for valve prosthesis implantation is typically made of nonabsorbable polyester. When the two ends of a single suture, are tied together, a 4-8 mm segment of the circumference of the valve ring and the circumference of the annulus, (the rim of heart tissue that remains after excision of the dysfunctional native valve, and to which the prosthesis is sutured) are compressed tightly together.
To decrease the likelihood of the suture pulling through the annular tissue as tension is applied during tying, most surgeons use pledgeted sutures. A xe2x80x9cpledgetxe2x80x9d is a small flat absorbent pad used to protect a wound. It is made from a piece of PTFE coated felt from a polyester material, through which both needles of the suture have been passed. The size of the pledget varies with a preferred size of 4xc3x978 mm. Sutures usually come pre-pledgeted from the manufacturer in multi-packs for valve implantation. When pledgeted sutures are used, generally both needles are passed through the annular tissue as the initial step in such a way that the pledget lies in direct contact with the tissue and helps to distribute the force supplied to the 4-8 mm of tissue that lies between the two points of suture penetration. When tied, the annular circumference is compressed between the suturing ring of the prosthesis and the pledget. Multiple sutures are required to create this fluid tight compressive force between the tissue and the prosthesis.
In order to prevent leakage of blood between the prosthetic valve and the tissue annulus post operatively, accurate spacing of the multiple discrete sutures is essential. Tight compression between the tissue and the prosthetic ring is readily achieved if the two ends of the mattressed sutures are tightly tied together. Peri-valvular leakage, when it occurs, is more commonly the result of an excessive distance separating two neighboring pledgets. As such, it is essential to pass the first needle (that is to say, the first of any given pair, the pair consisting of the two ends of a single suture) through the annulus as close as possible to the second suture of the neighboring pair. This must be accomplished, however, without actually piercing the preceding suture. Valve sutures are a braided multifilament material and it is possible to pass one suture around or through the interstices of the neighboring strand. Although not always readily apparent at the time, this passing of one suture through the interstices of the adjacent strand may result in suture breakage when the sutures are tied, or in poor seating of the valve due to unevenly distributed tension.
To ensure that the entire circumference of the prosthesis is seated in the annulus in a fluid tight fashion, multiple sutures are required. If the diameter of the annulus is 29 mm, which is quite common in mitral valve replacement, and the mattress sutures are placed such that each encompasses 5 mm of annulus, approximately 18 discrete mattress sutures are required which involves passing 36 needles initially through the tissue, and subsequently through the suturing ring. As described above, every other stitch is technically more demanding and slightly more time consuming because of the increased precision required to pass extremely close to the preceding suture but without piercing it. As space is often quite limited when working inside the heart, the entire exercise can be very demanding. There is thus a continued need to provide improved suture devices and systems to accommodate small incisions associated with minimally invasive surgery and to simplify procedures for the implantation of prosthetic valves.
The invention consists of a configuration whereby a plurality of double-stranded needles are connected in sequence with a single-strand needle at each end. Each double-stranded needle incorporates two suture strands or threads on a single needle. In a preferred embodiment, the suture strands can alternate in color. Thus any given pair of needles are connected by a first strand of a first color and the next needle is connected with a second strand of a second color. A plurality of pledgets can be provided on the strands and can be arranged in a xe2x80x9cdaisy chainxe2x80x9d configuration with a single pledget or pad positioned between each pair of needles in the chain.
In a preferred embodiment, the suture system of the present invention may contain several co-braided monofilament suture strands, where two suture strands of different colors, such as green and white, are co-braided into a single suture strand creating a third suture color or striped suture. This additional color suture provides differentiation between the other suture strands and acts as a visual indicator when tying off the sutures.
The needle to double suture ratio is greater than 1:1 but does not exceed 3:1. This needle to double suture ratio is defined as the ratio of the needle wire diameter to twice the diameter of the suture. Thus, the needle is at least as large in crossection as the strands being drawn through tissue by the needle.
The suture system of the present invention results in a significant reduction and more particularly a reduction of between about forty to fifty percent (40-50%) in the number of needles and steps required to implant a prosthetic heart valve, and also reduces the time required for the procedure and the incidence of suturing errors. The suture system of the present invention provides many advantages to a surgeon. The surgeon can achieve proper spacing of the adjacent sutures which reduces the risk of peri-valvular leakage or interstitial bleeding that can occur as a result of using the interrupted sutures of the prior art. Further, there is a reduced risk for the needle to damage the adjacent suture as a result of trying to achieve the exact placement of the adjacent sutures that can occur with the interrupted suture technique. As the suture system of the present invention is provided with an alternating color such as a green and white suture strands and the option of using a third color suture positioned within the suture chain, confusion in determining which pairs of suture strands tie together is also substantially reduced. The spacing between two pledgets does not exceed 1-2 mm and more preferably, the pledgets are in abutting contact with each other.
Another preferred embodiment of the present invention includes a method to implant a valve prosthesis using the suture system of the present invention. The method begins, for example, by making a partial or full median sternotomy, thoracotomy or parasternal incision. In this embodiment, the patient is placed on a cardiopulmonary bypass so that the heart can be stopped. The diseased valve is then accessed and excised, and the prosthetic valve then sutured using the suture system of the present invention.
The method further comprises placing the first suture in the tissue using a single-stranded or armed needle. The next double-stranded needle is then taken and a second stitch is placed in the annulus of the valve site approximately 4-6 mm from where the first stitch was placed. Because the second needle is double-stranded, the second stitch places the second stitch of the first suture along with the first stitch of the second suture. The following sutures are placed using the double-stranded needles, 4-6 mm from the previous suture placement until the entire circumference of the valve annulus has been sutured.
Once the entire circumference of the valve annulus has been sutured, the prosthetic valve is sutured. The prosthetic valve is held approximately 5 cm above the valve annulus during suturing. The sutures are placed through the cuff of the prosthetic valve using first a single-armed or stranded needle to place the first suture and then using the double-stranded needles placed through the cuff so that the pairs of sutures are evenly spaced around the circumference of the cuff. The prosthetic valve is aligned with the valve annulus. Once the sutures have been placed around the entire circumference of the cuff, the valve is lowered into position, the needles are cut off the sutures and the sutures are tied. The optional third color suture aids in tying off the sutures by acting as an additional visual indicator to differentiate between the suture strands associated with each pad or pledget. The prosthetic valve is then tested and the incision is closed.
The suture system of the present invention has different applications for many commonly performed medical procedures. For example, the suture system can be used in surgical procedures to correct ventricular aneurysms, atrial septal defects, and ventricular septal defects. Further, the suture system of the present invention can be used in procedures such as implanting of left ventricular assist devices. Aortic and mitral valve annuloplasty can also use the suture system of the present invention. In a preferred embodiment mechanical or electromechanical systems can be used in holding or manipulating the sutures during surgery.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.